The invention relates to an adjusting device, in particular for adjustment of a camshaft of an internal combustion engine.
An adjusting device is already known for adjustment of a camshaft of an internal combustion engine, with a brake unit which has at least one brake disc, and with at least one electromagnet for actuating the brake unit, the electromagnet having a yoke and an armature formed separately from the brake disc.
The object of the invention in particular is to provide a particularly reliable brake unit for an adjusting device, in particular for adjusting a camshaft of an internal combustion engine.
The starting point for the invention is an adjusting device, in particular for adjustment of a camshaft of an internal combustion engine, with a brake unit which has at least one brake disc, and with at least one electromagnet for actuating the brake unit, the electromagnet having a yoke and an armature formed separately from the brake disc.
It is proposed that the brake disc is disposed at least partially spatially between the yoke and the armature of the electromagnet. Due to an armature formed separately from the brake disc, the brake disc may be designed to be particularly thin, so that the inertia of the brake disc as well as a time constant of the controller can be reduced. Because the brake disc is disposed spatially between the yoke and the armature, the electromagnet can be designed as a pull magnet which has few parts in particular by comparison with a push magnet, so that a particularly compact, cost-effective and reliable brake unit can be provided. A “coil” of an electromagnet should be understood in particular to be a component with a wound electrical conductor which is provided so that, at least in an activation state of the brake unit, an electric current flows through it and a magnetic field is generated. A “yoke” of an electromagnet should be understood in particular to be a magnetic conductor which is surrounded at least in a region by the coil and which is disposed immovably with respect to the coil and in particular is provided in order to conduct the magnetic field of the coil. An “armature” of an electromagnet should be understood in particular to be a movably mounted magnetic conductor which is provided in order to be moved by a force produced by the magnetic field of the coil. “Provided” should be understood in particular to mean especially ‘designed,’ ‘equipped,’ and/or ‘disposed.’
Furthermore, it is proposed that the armature and the yoke each have at least one friction surface which are each provided in order to exert, at least in an activation state of the brake unit, a force on the brake disc. Because both the yoke and the armature exert a force on the brake disc, a particularly effective braking device can be provided. A “friction surface” should be understood in particular to be a surface which is provided in order to be, at least in an activation state of the brake unit, in contact with a corresponding surface of the brake disc, so that a braking force is generated which counteracts a rotary movement of the brake disc. The friction surface preferably has a brake lining which is provided in order to increase the generated braking force. The friction surface of the armature and the friction surface of the yoke are preferably disposed on different sides of the brake disc in a mirror image and facing one another relative to the brake disc. Particularly preferably the friction surfaces are congruent with one another, i.e. they have an identical shape.
Furthermore it is proposed that the forces exerted on the brake disc by the yoke and the armature are opposed to one another. In this way, axial forces on the brake disc can be avoided. Any effects of tolerances, thermal expansion and occurring wear can be compensated for and the durability of the brake unit can be increased. The fact that the forces exerted on the brake disc “are opposed to one another” should in particular be understood in this context to mean that, in an activation state of the brake unit, these forces impinge on two directly opposing surfaces of the brake disc and are oriented antiparallel relative to one another. The brake disc is preferably supported so as to be axially movable, so that the force of the yoke acts as an opposing force to the force of the armature acts, i.e. the force of the yoke and the force of the armature have the same value.
Furthermore it is proposed that the yoke and the armature are disposed on opposing sides of the brake disc. As a result a residual gap between the yoke and the armature is unnecessary for compensation for tolerances and wear, and the yoke, the brake disc and the armature are in contact with one another at an operating point of the electromagnet, so that the degree of efficiency of the brake is increased. The fact that the yoke and the armature are disposed on “opposite sides” of the brake disc should in particular be understood to mean that they lie opposite one another in the axial direction with regard to the brake disc and have the same radial spacing from the axis of the brake disc, and a radius from the axis to the yoke is disposed parallel to a radius from the axis to the armature.
Furthermore it is proposed that the brake disc has at least one annular friction surface which, at least in an activation state of the electromagnet, at least in a section is penetrated at least substantially in a straight line by a magnetic flux. In this way the brake disc can be of particularly lightweight construction as the brake disc does not have to perform the function of a magnetic armature, so that the inertia of the brake disc can be decreased and a time constant when adjusting the camshaft can be reduced. The fact that the brake disc is penetrated “in a straight line by a magnetic flux” should in particular be understood to mean that, in an activation state of the brake unit, the yoke and the armature have a magnetic circuit, i.e. that a magnetic flux through a cross-section of the armature is at least substantially equal to a magnetic flux through a cross-section of the yoke. A radial component of the magnetic flux in the brake disc is preferably less than 10% of an axial component of the magnetic flux and particularly advantageously less than 5% of the axial component of the magnetic flux.
Furthermore it is proposed that the brake disc is formed at least in the region of the friction surface from a ferromagnetically soft material. In this way a magnetic resistance of the brake unit can be decreased and the degree of efficiency of the brake unit can be increased. Moreover a permanent magnetization of the brake disc and thus an undefined residual brake torque can be avoided in a non-active state of the brake unit. A “ferromagnetic material” should in particular be understood to be a material which has a high magnetic conductivity. The material preferably has a magnetic permeability greater than 10000, particularly advantageously the material has a magnetic permeability greater than 100000. A “ferromagnetically soft material” should in particular be understood to be a material which has a low residual magnetization and thus a low coercive field strength. The coercive field strength is preferably less than 2 A/m, particularly advantageously less than 1 A/m.
Furthermore it is proposed that the brake disc has at least one second friction surface and an insulation region which spatially separates the friction surfaces and is formed from a magnetically non-conductive material. As a result a radial component of the magnetic flux in the brake disc and thus a unilateral force between the yoke and the brake disc can be reduced. In this context an insulation region should be understood in particular to be an annular region which is disposed in the radial direction between two annular friction surfaces of the brake disc. A “magnetically non-conductive material” should be understood to be a diamagnetic or paramagnetic material, for example austenitic stainless steel or aluminum.
Furthermore it is proposed that the brake disc has at least one spoke in the insulation region. As a result a particularly lightweight brake disc can be provided and a radial component of the magnetic flux can be reduced. In principle it is also conceivable that the brake disc is closed in the insulation region and is particularly thin.
Furthermore it is proposed that the armature of the electromagnet is designed as a hinged armature. In this way a particularly simply designed and cost-effective brake unit can be provided. A “hinged armature” should be understood to be an armature which is rotatably mounted on one end and has an axis of rotation which is disposed in a circumferential direction of the brake disc. The hinged armature is preferably mounted in the yoke of the electromagnet and has a planar arm which is disposed substantially parallel to the brake disc.
Furthermore it is proposed that the yoke of the electromagnet has at least one arm which covers the brake disc in the radial direction. In this way a particularly compact adjusting device can be provided. The arm of the yoke has on an open end a bearing in which the hinged armature of the brake unit is supported. In principle it is conceivable that the yoke has further arms which are preferably disposed offset from one another in a circumferential direction of the brake disc.
Furthermore a restoring element is proposed which is provided in order to exert a force on the yoke and the armature which is opposed to a force exerted by the yoke and the armature on the brake disc. In this way a residual brake torque can be minimized, so that the precision and reliability are increased when the adjusting device is used. A restoring element should be understood in particular to be an elastically deformable spring element which provides a tensioning force and is disposed functionally between the yoke and the armature.
Furthermore a valve train device for an internal combustion engine is proposed, with at least one camshaft and an adjusting device according to the invention which is provided for adjustment of the at least one camshaft. The controllability of the internal combustion engine can be improved by the use of the adjusting device in a valve train device.
Further advantages can be seen from the following description of the drawings. Two exemplary embodiments of the invention are shown in FIGS. 1 to 3. FIGS. 1 to 3, the description of the drawings and the claims contain numerous features in combination. Expediently, the person skilled in the art will also consider the features singly and combine them to form meaningful further combinations.